Ammonium salt lattice with isomorphously substituted inorganic salts



United States Patent 3,269,879 AMMONIUM SALT LATTICE WITH ISOMOR- PHOUSLY SUBSTITUTED INORGANIC SALTS Manfred Stammler, Carmichael, and Wilfred G. Schmidt,

Sacramento, Calif., assignors to Aerojet-General Corporation, Azusa, Calif., a corporation of Ohio No Drawing. Filed Apr. 13, 1964, Ser. No. 359,511 16 Claims. (Cl. 1492) This invention relates to novel isomorphous ammonium perchlorate and ammonium nitrate compositions prepared by cocrystallization, having greater sensitivity to impact and lower decomposition temperature, and being especially useful in explosive compositions, and to the method of producing the same.

An explosive in the broadest sense, is a material which, under the influence of shock, decomposes rapidly and spontaneously with evolution of large amounts of heat and gas. The hot gases create extremely high pressure if the explosive is set off in a confined space. Today, explosives are used to perform many engineering feats which would be physically or economically impossible without their use. Many diiferent types of explosives have been employed for these purposes. Explosives vary widely in their sensitivity and power. Ordinarily explosives are classified in one of the following three catagories; initiating explosives such as mercury fulminate and lead azide; high explosives such as cyclo-trimethylenetrinitramine (RDX); and low explosives such as black powders.

The initiating explosives are quite sensitive materials which can be made to explode by the application of fire or by means of a slight blow. Initiating explosives are generally used in primers and detonators. High explosive materials are those capable of exploding with great violence when set oil by an explosive shock such as that which would be obtained by detonating a small amount of initiating explosive in contact with the high explosive. The low explosives diifer in their mode of decomposition from the other two types, in that they only burn, and thus their action is less shattering.

The bulk of the explosives employed industrially in the United States in mining and construction work is of the high explosive type. However, many of the high explosives commonly used, such as RDX, are relatively expensive. Dherefore, lower cost ingredients for high explosive compositions are needed. Ammonium perchlorate and ammonium nitrate are well-known as oxidizer materials for use in solid rocket propellants. However, these materials are relatively insensitive to impact, thus limiting their use in high explosive compositions. It has now been found, however, that the sensitivity to impact of ammonium perchlorate and ammonium nitrate can be increased to a level approximately corresponding to that possessed by RDX. This has now been accomplished by cocrystallizing ammonium perchlorate and ammonium nitrate with certain other inorganic salts. These cocrystallized salts are isomorphous in nature and possess greater sensitivity to impact.

It is therefore an object of this invention to provide ammonium perchlorate and ammonium nitrate compositions possessing substantially enhanced impact sensitivity. Still another object of this invention is to increase the low temperature decomposition rate of ammonium nitrate and ammonium perchlorate. More specifically, it is an object of this invention to provide novel impact sensitive compositions containing a lattice of ammonium perchlorate or ammonium nitrate and containing isomorphously substituted therein certain inorganic salts. These and other objects of this invention will become apparent from the detailed description which follows.

. There has been found according to this invention novel impact sensitive compositions comprising a lattice selected from the group consisting of ammonium perchlorate and ammonium nitrate, and substituted in said lattice inorganic salts isomorphously co-crystallizable therewith. These inorganic salts are sometimes hereinafter referred to as substituent salts.

The inorganic salts capable of undergoing cocrystallization with ammonium perchlorate to form isomorphous compositions include those having the formula:

w'herein M is an alkali or alkaline earth metal cation, or the ammonium (NH group, and has a valence numerically equal to 12"; and X is an anion selected from the group consisting of chromate, iodate, periodate and permanganate, and has a valence numerically equal to a. Subscripts a and b are small whole numbers of from 1 to about 3. Compounds within the scope of Formula I include sodium chromate, lithium iodate, potassium periodate, calcium permanganate, strontium chromate, magnesium iodate, barium chromate, ammonium chromate, ammonium periodate and ammonium permanganate.

Another class of compounds which can be effectively cocrystallized with ammonium perchlorate are those having the formula:

(II) M' X' wherein M' is a thallium, silver or copper cation; the valence of M is equal numerically to d; X is an anion selected from the group consisting of perchlorate, chromate, iodate, periodate and permanganate; and has a valence equal to c. Subscripts c and d are small integers, usually equal to 1, 2 or 3. Compounds of the type defined by Formula II include thallium perchlorate, silver iodate, copper periodate, silver chromate, thallium iodate, copper permanganate and silver perchlorate.

The ammonium nitrate is cocrystallized with compounds of the formula:

(III) M" X";

wherein M" is a cation selected from the group consisting of silver, thallium, copper, or an alkali metal such as potassium, lithium or sodium. The valence of M" numerically equals the value of f. In this formula, X" is an anion having a valence equal to e and is selected from the group consisting of nitrate, permanganate and ZO where Z" is halogen, preferably chlorine, bromine or iodine; and e and f are integers of from 1 to about 3. The inorganic salts capable of being cocrystallized with ammonium nitrate and defined by Formula III, include silver nitrate, thallous nitrate, potassium permanganate, potassium chlorate, potassium br'omate and potassium iodate.

In Table I there appears illustrative isomorphous compositions within the scope of our invention.

TAB LE I Lattice substituent Salt Sodium Chromate. Potassium Chromate.

. Calcium Iodate.

Potassium Periodate.

Copper Permauganate.

Thallium Perchlorate. Silver Chromate. Potassium Iodate. Magnesium Periodate. Potassium Permanganate. Silver Nitrate.

Thallous Nitrate. Potassium Permanganate. Potassium Chlorate. Potassium Bromate. Potassium Iodate.

Amiionium Perehlorate The substituent inorganic salts are normally .present in the isomorphous cocrystallized compositions in the 1 amount of from about 0.1 percent to about percent by weight and more preferably from about 0.5 percent .to about 2 percent by weight, based on the total weight of the cocrystallized product. The final isomorphous cocrystallized product is in a single phase and has an average particle size of from about 20 microns to about 700 microns.

Normally, the cocrystallization is carried out by first dissolving the ammonium perchlorate or ammonium nitrate and the inorganic salt to be cocrystallized therewith in water, and thoroughly mixing the solution. At least some of the water is then removed by heating and/or the application of reduced pressure until cocrystallization occurs. Preferably, this concentration procedure is carried out at a temperature of from about 20 C. to about 100 C., and at a pressure of from about 0.01 to about 1 atmospheres.

The weight ratio of total salts to water in the aqueous solution prior to concentration may be varied over a wide range and is not critical. Generally there should be initially present suflicient water to dissolve all of the salts. It can be seen that the minimum amount of water required for a given weight of salts will depend on the solubility of the salts and the mixing temperature being employed, and thus is readily ascertained by those skilled in the art. Ordinarily, the amount of water used will be somewhat in excess of the minimum amount, and will be from 0.2 to about 20 times the weight of the total salts. While the foregoing discussion is limited to the use of water as to the solvent, it is to be understood that any substantially inert solvent in which the salts are at least somewhat soluble may be utilized. Illustrative of other suitable solvents are the lower alkanols such as methanol and ethanol, and .the lower alkylene glycols such as ethylene glycol and propylene glycol.

After concentration the product is recovered in conventional manner by filtration, decantation and the like.

The following are illustrative examples demonstrating the preparation of the isomorphous cocrystallized compositions of this invention. These examples are provided solely for the purpose of illustration and are not to be regarded as limiting the scope of the invention in any way. In the examples the parts are by weight unless otherwise indicated.

EXAMPLE I cocrystallized ammonium perchlorate and potassium permanganate A 490 grams sample of ammonium perchlorate was dissolved in about 3 liters of water. The solution was poured into a 3-neck flask provided with a stirrer, thermometer and a dropping funnel. A solution of 10 grams of potassium permanganate in 500 ml. of water was then slowly added to the aqueous ammonium perchlorate solution. The vigorously stirred mixture was then concentrated at 50 C. under reduced pressure. When a thick slurry was obtained, the precipitate was filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the above-described method was analyzed for concentration of the inorganic salt chemically. The results are as follows:

NH ClO -KMnO 1.92 percent by weight KMnO tound.

EXAMPLE II Cocrystallized ammonium perchlorate and calcium chromate A 490 gram sample of ammonium perchlorate was dissolved in about 3 liters of water. The solution was poured into a 3-neck flask provided with a stirrer, thermometer and a dropping funnel. A solution of 10 grams of calcium chromate in 500 ml. of water was then slowly added to the aqueous ammonium perchlorate solution. The vigorously stirred mixture was then concentrated at 50 C. under reduced pressure. When a thick slurry NH C-lO -CaOrO 2.03 percent by weight CaCrO tfound.

EXAMPLE HI Cocrystallized ammonium perchlorate and potassium iodate A 490 gram sample of ammonium perchlorate was dis solved in about 3 liters of water. The solution was poured into a 3-neck flask provided with a stirrer, thermometer and a dropping funnel. A solution of 10 grams of potassium iodate in 500 ml. of water Was then slowly added to the aqueous ammonium perchlorate solution. "The vigorously stirred mixture was then concentrated at 50 C. under reduced pressure. When a thick slurry was obtained, the precipitate was filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the above-described method was analyzed and found to contain about two percent potassium iodate.

EXAMPLE IV Cocrystallized ammonium perchlorate and potassium periodate A 490 gram sample of ammonium perchlorate was dis solved in about 3 liters of water. The solution was poured into a 3-neck flask provided with a stirrer, thermometer and a dropping funnel. A solution of 10 grams of potassium perchlorate in 500 of water was then slowly added to the aqueous ammonium periodate solution. The vigorously stirred mixture was then concentrated at 50 under reduced pressure. When a thick slurry was obtained, the precipitate was filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the above-described method was analyzed for concentration of the inorganic salt chemically, and found to contain about 2 percent by weight of potassium perioda-te.

EXAMPLE V Cocrystallized ammonium perchlorate and thallium perchlorate A 490 gram sample of ammonium perchlorate was dissolved in about 3 liters of water. The solution was poured into a 3-neck flask provided with a stirrer, thermometer and a dropping funnel. A solution of 10 grams of thallium perchlorate in 500 ml. of water was then slowly added to the aqueous ammonium perchlorate solution. The vigorously stirred mixture was then concentrated at 50 C. under reduced pressure. When a thick slurry was obtained, the precipitate was filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the above-described method was analyzed for concentration of the inorganic salt and found to contain about two percent by weight of thallium perchlorate.

EXAMPLE VI Cocrystallized ammonium nitrate and potassium iodate About 500 grams of ammonium nitrate are dissolved in about 5 liters of water. The solution is poured into a flask provided with a stirrer, thermometer and a dropping funnel. A solution of about 10 grams of potassium iodate in 500 ml. of water is then slowly added to the aqueous ammonium nitrate solution. The vigorously stirred mixture is then concentrated at about 40 to 50 C. under reduced pressure. When a thick slurry is obtained, the precipitate is filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the above-described method is analyzed for concentration of the inorganic salt, and found to contain about two percent by weight of potassium iodate.

The product is found to be substantially more impact sensitive than pure ammonium nitrate.

EXAMPLE VII Cocrystallized ammonium nitrate and silver nitrate A 500 gram sample of ammonium nitrate is dissolved in about 4 liters of water. The solution is poured into a flask provided with a stirrer, thermometer and a dropping funnel. A solution of about grams of silver nitrate in about 1000 ml. of water is then slowly added to the aqueous ammonium nitrate solution. .The vigorously stirred mixture is then concentrated at about 60 C. under reduced pressure. When a thick slurry is obtained, the precipitate is filtered, dried and screened, to obtain an isomorphous cocrystallized product. The product obtained by the about-described method is analyzed for concentration of the inorganic salt, and found to contain about two percent by weight of silver nitrate.

The elfect of the inorganic su'bstituent salt in the cocrystalline product on the impact sensitivity of ammonium perchlorate is demonstrated by the data appearing in the following table. The sensitivity numbers appearing in the table refer to the drop height of a 2 kilogram weight at which 50 percent of the trials resulted in an explosion.

TABLE II Impact sensitivity Composition: (centimeters) RDX 33 NH ClO (pure) 100 NH ClO +2% KMnO (mechanical mixture) 100 NH ClO -2% KMnO (cocrystallized) (Composition I from Table I) 75 NH ClO -2% K10 (cocrystallized) (Composition D from Table I) 27 NH ClO -2% K10 (cocrystallized) (Composition H from Table I) 50 As can be seen from the foregoing table, the isomorphously substituted ammonium perchlorate of the present invention possesses a substantially increased impact sensitivity when compared to pure ammonium perchlorate, or to a mechanical mixture of ammonium perchlorate and the inorganic salt. The foregoing data also demonstrate that by the practice of the present invention, it is possible to prepare isomorphously substituted ammonium perchlorate compositions possessing an impact sensitivity of the same order of magnitude as RDX.

The rate of decomposition of pure, mechanical mixtures, and isomorphously substituted ammonium perchlorate was investigated using a thermogravimetric balance. All experiments were carried out at atmospheric pressure, and all of the samples used were of 325 Tyler mesh. The sensitivity of the method is such that a weight loss as loW as 0.5 weight percent of the sample can be measured.

TAB LE III Heating Heating Temp, Time, 0. Min.

Weight No. Composition percent NH ClO -2% CaCrOw NH ClO +2% CaCrO B Cocrystallized. b Mechanical mixture. 0 Pure.

Referring to Table III, it can be seen that-the cocrystallized material of Run 1 decomposed far more readily than the mechanical mixture of Run 2. Comparison of Runs 3 through 6 with Runs 7 through 10 shows that the cocrystallized material is also quicker to decompose than is pure ammonium perchlorate. Run 11 demonstrates that a cocrystallized material containing potassium permanganate will decompose almost completely when heated for 20 minutes at 176 C. In contrast thereto, the mechanical mixture of Run 12 underwent only an 8.0 percent decomposition after prolonged heating (60 minutes) at 208 C.

The illustrative examples and data set forth above clearly show that the novel cocrystallized compositions of our invention possess greater impact sensitivity and will decompose more readily than ordinary ammonium perchlorate and ammonium nitrate. Thus, the compositions of our invention will find many uses in the field of high explosives, as will be apparent to those skilled in the art.

Having fully described our invention, it is intended that it be limited only by the lawful scope of the appended claims and a reasonable range of equivalents.

We claim:

1. A novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously substituted therein an inorganic salt selected from the group consisting of those having the formula:

wherein M is a cation selected from the group consisting of alkali metals, alkaline earth metals and the ammonium group, X is an anion selected from the group consisting of chromate, iodate, periodate and permanganate, and a and b are small whole numbers of from 1 to about 3; and those having the formula:

wherein M is a cation selected from the group consisting of thallium, silver and copper, X is an anion selected from the group consisting of perchlorate, chromate, iodate, periodate and permanganate, and c and d are small whole numbers of from 1 to about 3.

2. The novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously sub stituted therein by cocrystallization, potassium permanganate.

3. The novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously substituted therein by cocrystallization, calcium chromate.

4. The novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously sub stituted therein by cocrystallization, potassium iodate.

5. The novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously substituted therein by cocrystallization, potassium periodate.

6. The novel composition of matter comprising an ammonium perchlorate lattice, and isomorphously substituted therein by cocrystallization, thallium perchlorate.

7. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, silver nitrate.

8. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, thallium nitrate.

9. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, potassium permanganate.

10. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, potassium chlorate.

11. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, potassium bromate.

12. The novel composition of matter comprising an ammonium nitrate lattice, and isomorphously substituted therein by cocrystallization, potassium iodate.

13. The method of preparing a novel composition of matter which comprises dissolving ammonium perchlorate in a solvent; adding to the solvent an inorganic salt selected from the group consisting of those having the formula:

wherein M is a cation selected from the group consisting of alkali metals, alkaline earth metals and the ammonium group, X is an anion selected from the group consisting of chromate, iodate, periodate and permanganate, and a and b are small whole numbers of from 1 to about 3; and those having the formula:

wherein M is a cation selected from the group consisting of thallium, silver and copper, X is an anion selected from the group consisting of perchlorate, chromate, iodate, periodate and permanganate, and c and d are small whole numbers of from 1 to about 3; removing at least some of the solvent until cocrystallization occurs; and then recovering the isomorphous cocrystallized product.

14. A novel explosive process comprising:

(a) providing an explosive charge comprising an ammonium perchlorate lattice, and isomorphously substituted therein an inorganic salt selected from the group consisting of those having the formula:

wherein M is a cation selected from the group consisting of alkali metals, alkaline earth metals and the ammonium group, X is an anion selected from the group consisting of chromate, iodate, periodate and permanganate, and a and b are small Whole numbers of from 1 to about 3; and those having the formula:

wherein M is a cation selected from the group consisting of thallium, silver and copper, X is an anion selected from the group consisting of perchlorate, chromate, iodate, periodate and permanganate, and c and d are small Whole numbers of from 1 to about 3, said inorganic salt serving as the sole sensitizing material for the ammonium perchlorate and being present in an amount within the range of about 0.1 to about 10% of the combined weight of the ammonium perchlorate and said inorganic salt; and (b) effecting an explosion of the explosive charge. 15. A composition of matter in accordance with claim 1 wherein the inorganic salt is provided in an amount within the range of about 0.1 to about 10% of the combined weight of the ammonium perchlorate and said inorganic salt.

16. A composition of matter in accordance with claim 15 wherein said inorganic salt is provided as the sole sensitizing material for the ammonium perchlorate.

References Cited by the Examiner UNITED STATES PATENTS 2,589,532 3/1952 Byers 1492 X 2,602,026 7/1952 Farr 149l7 X 2,993,767 7/1961 Berl et al. 14946 X 3,030,179 4/1962 McFarlin et al. 149-46 X 3,173,756 3/1965 Griffith 149-46 X BENJAMIN R. PADGETT, Acting Primary Examiner. 

1. A NOVEL COMPOSITION OF MATTER COMPRISING AN AMMONIUM PERCHLORATE LATTICE, AND ISOMORPHOUSLY SUBSTITUTED THEREIN AN INORGANIC SALT SELECTED FROM THE GROUP CONSISTING OF THOSE HAVING THE FORMULA: 